Golf balls can generally be divided into two classes: solid and wound. Solid golf balls include one-piece, two-piece (i.e., solid core and a cover), and multi-layer (i.e., solid core of one or more layers and/or a cover of one or more layers) golf balls. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by tensioned elastomeric material, and a cover. Solid balls have traditionally been considered longer and more durable than wound balls, but also lack the particular “feel” that is provided by the wound construction and typically preferred by accomplished golfers.
By altering ball construction and composition, however, manufacturers can vary a wide range of playing characteristics, such as resilience, durability, spin, and “feel,” each of which can be optimized for various playing abilities, allowing solid golf balls to provide feel characteristics more like their wound predecessors. The golf ball components, in particular, that many manufacturers continually look to improve are the center or core, intermediate layers, if present, and covers.
The core is the “engine” of the golf ball when hit with a club head. Generally, golf ball cores and/or centers are constructed with a polybutadiene-based polymer composition. Compositions of this type are constantly being altered in an effort to provide a targeted or desired coefficient of restitution (“COR”) while at the same time resulting in a lower compression which, in turn, can lower the golf ball spin rate, provide better “feel,” or both. This is a difficult task, however, given the physical limitations of currently-available polymers. As such, there remains a need for novel and improved golf ball core compositions.
Manufacturers also address the properties and construction of golf ball intermediate and cover layers. These layers have conventionally been formed of ionomer materials and ionomer blends of varying hardness and flexural moduli. This hardness range is still limited and even the softest blends suffer from a “plastic” feel according to some golfers. Recently, however, polyurethane-based materials have been employed in golf ball layers and, in particular, outer cover layers, due to their softer “feel” characteristics without loss in resiliency and/or durability.
A known drawback of polybutadiene cores cross-linked with peroxide and/or zinc diacrylate is that this material is adversely affected by moisture. Water moisture vapor reduces the resiliency of the cores and degrades its properties. A polybutadiene core will absorb water and lose its resilience. Thus, these cores must be covered quickly to maintain optimum ball properties. The cover is typically made from ionomer resins, balata, and urethane, among other materials. The ionomer covers, particularly the harder ionomers, offer some protection against the penetration of water vapor. However, it is more difficult to control or impart spin to balls with hard covers. Conventional urethane covers, on the other hand, while providing better ball control, offer less resistance to water vapor than ionomer covers.
Prolonged exposure to high humidity and elevated temperature may be sufficient to allow water vapor to invade the cores of some commercially available golf balls. For example at 110° F. and 90% humidity for a sixty day period, significant amounts of moisture enter the cores and reduce the initial velocity of the balls by 1.8 ft/s to 4.0 ft/s or greater. The change in compression may vary from 5 PGA to about 10 PGA or greater. The absorbed water vapor also reduces the coefficient of restitution (COR) of the ball.
Despite attempts by manufacturers at limiting vapor transmission to the core, there remains a need for other golf balls with an improved water vapor barrier layer and improved methods for applying a water vapor barrier layer on to the core of the golf ball.
Ormocers, for example, are a relatively new class of composite materials formed of ceramic and polymer networks that combine and interpenetrate with one another. Many names have been given to these materials, such as ceramers, polycerams, ormosils, and ormocers, depending on the scientific background of the naming party (i.e., polymers scientists, glass or ceramic scientists, organometallic scientists).
Ormorcer is an acronym for ORganically MOdified CERamics. These materials represents a novel inorganic-organic copolymer in the formulation that allows for modification of its mechanical parameters. Ormocers not only have relatively high chemical and mechanical stability; they also open up opportunities to adjust the porosity and chemical functionalization of resulting products. Ormocers (also referred to as ceramers, ormosils, and hybrids) are composites with organic and inorganic nano-building blocks linked most often via stable covalent bonds based on organically modified silicon oxides and/or functionalized organic oligomers/polymers.
The inorganic-organic copolymers are typically synthesized from multi-functional urethane- and thioether(meth)acrylate alkoxysilanes as sol-gel precursors. Alkoxysilyl groups of the silane permit the formation of an inorganic Si—O—Si network by hydrolysis and poly-condensation reactions. The methacrylate groups are available for photochemical or thermal polymerization. Vinyl and epoxy groups can also be polymerized into the siliceous network. These and other novel hybrid materials described herein are investigated for use in a variety of golf ball components that include, but are not limited to, golf ball centers, cores, layers, covers, and coating materials and/or blends, continuous or non-continuous layers, thick or thin films, vapor barrier layers, fillers, fibers, flakes, windings, adhesives, coupling agents, compatibilizers, composites, reinforcements, and inks.
The present invention is directed to golf balls having components, in particular vapor barrier layers, formed of novel hybrid materials, such as glass ionomers, ormocers, and other inorganic-organic materials.